Drag and drop and selecting pad for editing can be done quite easily.
The challenge is how to trigger the sample from the pad.

I found a clumsy workaround to trigger the sample by misusing the Drum Player module. But it's far from ideal. It would be much easier if Halion allowed creating midi note on messages in controller thread or allowed access to its internal keyboard to somehow link a switch on the macro page with a key of its keyboard.